[0001] This disclosure relates to a capacitive touch sensor device and a controller for
a capacitive touch sensor.
[0002] Capacitive touch sensor devices are known in the art. A capacitive touch sensor device
includes electrodes coupled to an inner surface of a touch panel. Touching of the
touch panel is detected from a change in the capacitance at each electrode. The capacitance
at each electrode may change when a finger approaches the electrode even though the
finger is not contacting the touch panel.
[0003] Japanese Laid-Open Patent Publication No.
2013-149199 describes a touch sensor device including a control unit that stores an OFF determination
threshold value used to determine whether or not a touched state has shifted to a
non-touched state. The control unit determines that the touch sensor device is in
a touched state when the capacitance of an electrode is greater than or equal to the
OFF determination threshold value and determines that the touch sensor device is in
a non-touched state when the capacitance is lower than the OFF determination threshold
value.
[0004] The capacitance of an electrode changes in accordance with the distance between a
finger and the electrode. The capacitance also changes in accordance with the size
of the finger that approaches the electrode. That is, the capacitance changes in accordance
with the area of the finger opposing the electrode. Accordingly, the change in capacitance
of an electrode differs between a user having large fingers and a user having small
fingers even if the distance between the finger and the electrode is the same. In
the conventional touch sensor device such as that described in the above publication,
the OFF determination threshold value stored in the control unit is a fixed value.
Accordingly, the distance between the touch panel and the finger for determining that
the touch panel is in a non-touched state differs between users. For example, even
if a user moves a finger away from the touch panel, the touch sensor device may continue
to determine that the touch panel is in a touched state. Thus, when using the conventional
touch sensor device, consecutive taps such as a double tap may not be correctly detected.
This may be frustrating to the user.
[0005] It is an object of this disclosure to provide a touch sensor device having improved
operation detection accuracy and a controller for such a touch sensor device.
[0006] One embodiment of this disclosure is a touch sensor device including an electrode
and a control unit. The electrode is located at an inner side of a touch panel. The
control unit is configured to detect a change in a capacitance generated at the electrode
when a finger approaches the electrode and determine whether or not the touch panel
has been touched from the change in the capacitance. The control unit is further configured
to detect a maximum capacitance generated at the electrode during detection of a touched
state and set a first OFF determination threshold value, which is used to detect a
non-touched state, to a value that is lower than the maximum capacitance by a predetermined
value which is set in advance.
[0007] The touch sensor device and the controller of this disclosure improve the operation
detection accuracy.
[0008] Other embodiments and advantages of this disclosure will become apparent from the
following description, taken in conjunction with the accompanying drawings, illustrating
by way of example the principles of the invention.
[0009] The invention, together with objects and advantages thereof, may best be understood
by reference to the following description of the presently preferred embodiments together
with the accompanying drawings in which:
Fig. 1 is a perspective view illustrating a passenger compartment of a vehicle in
which a touch sensor device is installed;
Fig. 2 is a schematic block diagram illustrating the touch sensor device;
Fig. 3 is a graph schematically illustrating the relationship of the panel-finger
distance and the electrode capacitance;
Fig. 4 is a graph illustrating one example of changes in the capacitance when the
touch panel is swiped;
Fig. 5 is a flowchart schematically illustrating the processing executed by a control
unit of the touch sensor device;
Fig. 6 is a graph illustrating changes in the capacitance when the touch panel is
double tapped; and
Fig. 7 is a schematic diagram of a touch sensor device and a touchpad in another example.
[First Embodiment]
[0010] A first embodiment of a touch sensor device will now be described with reference
to the drawings.
[Configuration of Touch Sensor Device]
[0011] As illustrated in Fig. 1, a vehicle includes a touch sensor device 10 used to input
information for controlling various devices such as the air conditioner.
[0012] As illustrated in Fig. 2, the touch sensor device 10 includes a touch panel 11, electrodes
12, and a control unit 13.
[0013] As illustrated in Fig. 1, the touch panel 11 is arranged in the dashboard. The touch
panel 11 has an outer surface that is exposed to the outer side. Further, the touch
panel 11 includes operated regions, which are operated to, for example, raise the
temperature, lower the temperature, increase the fan speed, decrease the fan speed,
change the direction of the air flow, switch to automatic air conditioning, and switch
to manual air conditioning. The touch panel 11 is formed by an insulator such as glass
or an acrylic resin.
[0014] As illustrated in Fig. 2, the electrodes 12 are adhered to the inner surface of the
touch panel 11 at locations corresponding to the operated regions. The touch panel
11 protects the electrodes 12 from the outer side. A parasitic capacitance (Cp) exists
between each electrode 12 and a reference potential (GND). When a conductor (e.g.,
user's fingertip) approaches or touches the touch panel 11, capacitance is generated
between the conductor and the electrode 12. Here, the capacitance generated at the
electrode corresponds to the sum (total capacitance) of the capacitance between the
conductor and the electrode 12 and the parasitic capacitance (Cp). Thus, the capacitance
at the electrode 12 changes (increases) when the finger approaches the electrode 12.
[0015] The control unit 13 is connected to the electrodes 12 by resistors R, respectively.
Thus, voltage corresponding to the capacitance generated at the electrode 12 is supplied
to the control unit 13. The control unit 13 receives the voltage corresponding to
the capacitance generated at each electrode 12 to determine whether or not the touch
panel 11 has been touched from changes in the capacitance. Although not illustrated
in the drawings, the control unit 13 is connected to controllers for various types
of devices such as an air conditioner and an audio device. Further, the control unit
13 provides each controller with a determination of whether or not the touch panel
11 was touched. The controller of each device controls the corresponding device based
on the determination.
[0016] The control unit 13 includes a memory 13a. The memory 13a stores an ON determination
threshold value that determines whether the touch panel 11 has shifted from a non-touched
state to a touched state. The control unit 13 compares an increase amount of the capacitance
at each electrode with the ON determination threshold value to detect shifting of
the touch panel 11 to a touched state. The ON determination threshold value is set
in advance through experiments or the like. For example, the control unit 13 determines
in a non-touched state whether or not expression (1), which is illustrated below,
has been satisfied. In expression (1), the "present value" refers to the presently
detected capacitance, and the "preceding value" refers to the preceding detected capacitance.
Accordingly, "(present value) - (preceding value)" refers to the increase amount of
the capacitance. When the increase amount of the capacitance is greater than the ON
determination threshold value, that is, when expression (1) is satisfied, the control
unit 13 determines that the touch panel 11 has shifted from a non-touched state to
a touched state and outputs the determination to the controller of each device.
[0017] The memory 13a stores a first OFF determination threshold value used to determine
whether or not the touch panel 11 has shifted from a touched state to a non-touched
state. In the present example, expression (2), which is illustrated below, is stored
in the memory 13a to calculate the first OFF determination threshold value. The control
unit 13 calculates the first OFF determination threshold value in a touched state
from expression (2). As illustrated in expression (2), the first OFF determination
threshold value is obtained by dividing the maximum capacitance by a given set value
(first predetermined set value). The maximum capacitance is the maximum value of the
capacitance detected during a touched state. The control unit 13 determines in a touched
state whether or not expression (3) has been satisfied, that is, whether or not the
present value is lower than the first OFF determination threshold value. When expression
(3) is satisfied, the control unit 13 determines that the touch panel 11 has shifted
from a touched state to a non-touched state and outputs the determination to the controller
of each device.
[Operation of Touch Sensor Device]
[0018] The operation of the touch sensor device 10 will now be described. It is known that
the finger has to be squeezed by about one to two millimeters for a person to acknowledge
a tactile perception of an object (here, touch panel 11). In contrast, as soon as
the finger is separated from the object, a person would acknowledge that the finger
is no longer touching the object (here, touch panel 11).
[0019] The operation of the touch sensor device 10 when determining that the touch panel
11 has shifted from a touched state to a non-touched state will now be described.
In the case described below, the first OFF determination threshold value is calculated
using the set value of "2".
[0020] The area of the fingertip opposing an electrode 12 differs between a user having
large fingers and a person having small fingers. Fig. 3 is a chart illustrating simulation
results with two graphs. One graph is obtained by plotting changes in the capacitance
when a person having large fingers touches the touch panel 11. The other graph is
obtained by plotting changes in the capacitance when a person having small fingers
touches the touch panel 11. As illustrated in Fig. 3, the capacitance generated at
an electrode 12 when the touch panel 11 is touched differs in accordance with the
size of the finger. In the present example, the control unit 13 sets the first OFF
determination threshold value to a value obtained by dividing the maximum capacitance
by the set value (here, two). Thus, regardless of whether the user's finger is small
or large, the control unit 13 determines that the touch panel 11 has shifted from
a touched state to a non-touched state when the finger is separated by approximately
the same distance from the touch panel 11. Hereafter, the distance from the touch
panel 11 to the separated finger will be referred to as "the finger separation distance".
As illustrated in the simulation results of Fig. 3, the differences in the finger
separation distance is approximately 0.3 mm to 0.5 mm. The difference in the finger
separation distance is smaller than when using a fixed OFF determination threshold
value like in the prior art. Thus, regardless of the finger size, the shifting from
a touched state to a non-touched state is determined from nearly the same finger separation
distance for any user.
[0021] The operation of the touch sensor device 10 when determining that a non-touched state
has shifted to a touched state will now be described.
[0022] As illustrated in Fig. 3, the increase rate (graph gradient) of the capacitance is
generally constant when the finger approaches the electrode 12 regardless of the finger
size. Thus, by comparing the increased amount of the capacitance with the ON determination
threshold value when a finger approaches and touches the touch panel 11, the shifting
of the touch panel 11 from a non-touched state to a touched state may be detected
at about the same squeezed finger amount regardless of the finger size.
[0023] In this manner, user characteristics, such as the size of the finger, have a smaller
influence than the prior art on the determination of the shifting from a touch state
to a non-touched state and vice-versa. This obtains high accuracy for the detection
of consecutive taps such as a double tap.
[0024] The first embodiment has the advantages described below.
- (1) The control unit 13 detects the maximum capacitance generated at an electrode
during a touched state in which the touch panel 11 is touched. Then, the control unit
13 sets the first OFF determination threshold value to a value that is lower than
the maximum capacitance by a predetermined value that is set in advance. In the present
example, the first OFF determination threshold value is set at a value obtained by
dividing the maximum capacitance by a first predetermined set value (e.g., two). The
maximum capacitance changes in accordance with the size of the finger that approaches
the electrode 12. As a result, the first OFF determination threshold value is set
in accordance with the size of the finger. In this manner, the first OFF determination
threshold value is dynamically set based on the present maximum capacitance, that
is, in accordance with the characteristics of the user using the touch sensor device
10. In contrast with the prior art, this reduces the influences resulting from the
characteristics of the user who is operating the touch sensor device 10 and improves
the operation detection accuracy.
- (2) The finger separation distance is substantially constant regardless of the finger
size. This improves the accuracy for detecting consecutive taps such as a double tap.
Thus, the touch panel 11 is easy to use.
- (3) The ON determination threshold value used to determine shifting from the non-touched
state to the touched state is set to a value that takes into consideration the increased
amount of the capacitance. In contrast with the prior art, this reduces the influences
resulting from the characteristics of the user operating the touch sensor device 10
and improves the operation detection accuracy.
- (4) The user characteristics have a smaller influence than the prior art on the determination
of the shifting from a touched state to a non-touched state and the determination
of the shifting from a non-touched state to a touched state. This improves the operation
detection accuracy of consecutive taps such as a double tap.
[Second Embodiment]
[0025] A second embodiment of a touch sensor device 10 will now be described.
[0026] Generally, touch operations include a short tap, a long tap, and a swipe. In the
first embodiment, the control unit 13 does not distinguish these operations in a more
preferable manner. When controlling a device, these operations (short tap, long tap,
and swipe) may have to be distinguished from one another. In the second embodiment,
the control unit 13 is configured to determine whether one of a short tap, a long
tap, and a swipe has been performed and output the determination. Except for the information
used to determine an operation, the control unit 13 of the second embodiment is configured
in the same manner as that of the first embodiment. Thus, same reference numerals
are given to those components that are the same as the corresponding components of
the first embodiment. Such components will not be described in detail.
[0027] As illustrated by the broken lines in Fig. 2, the memory 13a of the control unit
13 stores a first operation determination time used to determine whether the touch
operation performed on the touch panel 11 is a short tap, a long tap, or a swipe.
The first operation determination time is a value compared with the time during which
a touched state is detected and is set in advance through experiments or the like.
[0028] Further, the memory 13a stores a second OFF determination threshold value used to
determine the shifting of the touch panel 11 from a touched state to a non-touched
state during swiping of the touch panel 11. The second OFF determination threshold
value is compared with the capacitance of an electrode 12 and set at a predetermined
value based on experiments or the like. Preferably, the second OFF determination threshold
value is set to be at least lower than the first OFF determination threshold value
and slightly higher than the total capacitance of every one of the electrodes 12 in
a non-touched state.
[0029] The control unit 13 also includes a time counter 14 that starts to measure time from
when the touch panel 11 is switched from a non-touched state to a touched state. That
is, the time counter 14 measures the time during which a touched state is detected
(hereinafter, also referred to as "touched state detection time"). The measurement
value of the time counter 14 is reset when the touched state shifts to the non-touched
state.
[0030] The control unit 13 determines whether or not a short tap has been performed based
on whether or not expression (4) has been satisfied.
[0031] When expression (4) is satisfied, the control unit 13 determines that a short tap
has been performed on the touch panel 11. In the determination of expression (4),
the determination of whether a touched state has shifted to a non-touched state, that
is, the detection of a non-touched state is performed in accordance with expression
(3), which is described above. Further, the control unit 13 obtains a touched position
when determining that a short tap has been performed. Then, the control unit 13 provides
the controller of each device with information indicating the short tap and information
indicating the touched position.
[0032] When expression (4) is not satisfied, the control unit 13 determines that a long
tap or a swipe has been performed on the touch panel 11. In this case, the control
unit 13 obtains two touched positions before and after the first operation determination
time elapses. Then, the control unit 13 compares the two touch positions.
[0033] When the two touched positions are the same, the control unit 13 determines that
a long tap has been performed on the touch panel 11. Then, the control unit 13 provides
the controller of each device with information indicating the long tap and information
indicating the touched position. The control unit 13 determines whether or not the
touch panel 11 is still in a touched state during the long tap based on whether or
not expression (3) is satisfied. When expression (3) is not satisfied, the control
unit 13 determines that a long tap is being continuously performed and provides the
controller of each device with information indicating the long tap and information
indicating the touched position. When expression (3) is satisfied, the control unit
13 determines that a long tap has been completed and provides the controller of each
device with information indicating completion of the long tap.
[0034] When the two touched positions obtained before and after the first operation determination
time elapses differ from each other, the control unit 13 determines that the touch
panel 11 has been swiped. Then, the control unit 13 provides the controller of each
device with information indicating the swipe and information indicating the touched
positions. In this case, the control unit 13 determines whether or not a touched state
is continuing during the swipe based on whether or not expression (5) is satisfied,
that is, whether or not the present value is lower than the second OFF determination
threshold value.
[0035] When expression (5) is not satisfied, the control unit 13 determines that the touch
panel 11 is still being swiped and provides the controller of each device with information
indicating the swipe and information indicating the touched positions. When expression
(5) is satisfied, the control unit 13 determines that the swipe has been completed
and provides the controller of each device with information indicating completion
of the swipe.
[Operation of Touch Sensor Device]
[0036] The operation of the touch sensor device 10 according to the second embodiment will
now be described.
[0037] The control unit 13 compares the first operation determination time stored in the
memory 13a with the time during which a touched state is detected to determine whether
or not a short tap has been performed. When a short tap is not performed, the control
unit 13 compares two touched positions before and after the first operation determination
time to determine whether a long tap or a swipe has been performed. Thus, the use
of the touch sensor device 10 according to the second embodiment allows a short tap,
a long tap, and a swipe to be distinguished from one another.
[0038] When the control unit 13 determines that the touch panel 11 is being swiped, the
control unit 13 determines whether the capacitance at the electrode 12 where the swipe
is being performed is greater than or equal to the second OFF determination threshold
value to determine whether the touch panel 11 is still being swiped.
[0039] Swiping is performed by moving a finger on the touch panel 11. Thus, the finger is
opposed to an electrode 12 for a very short period of time. Accordingly, the capacitor
at the electrode 12 where swiping is performed is not sufficiently charged. Thus,
when determining whether or not the touch panel 11 is still being swiped based on
the first OFF determination threshold value, the control unit 13 may determine that
the swiping has ended even though the touch panel 11 is actually still being swiped.
Taking this into consideration, the control unit 13 determines whether or not the
touch panel 11 is still being swiped based on the second OFF determination threshold
value ("non-touched determination threshold value" in Fig. 4), which is lower than
the first OFF determination threshold value, as illustrated by double-dashed lines
in Fig. 4. This allows for swiping to be detected in a desirable manner.
[0040] In addition to the advantages of the first embodiment, the second embodiment has
the advantages described below.
(5) The control unit 13 compares the first operation determination time with the touched
state detection time to determine whether or not a short tap has been performed. The
control unit 13 compares two touched positions before and after the first operation
determination time elapses to determine whether a long tap has been performed or whether
a swipe has been performed. This allows for a short tap, a long tap, and a swipe to
be distinguished from one another in a more preferable manner.
(6) The memory 13a of the control unit 13 stores the second OFF determination threshold
value that is lower than at least the first OFF determination threshold value and
slightly higher than the total capacitance of every one of the electrodes in a non-touched
state. The control unit 13 determines whether or not the touch panel 11 is still being
swiped based on the second OFF determination threshold value. This allows the control
unit 13 to detect a swipe in a desirable manner.
[Third Embodiment]
[0041] A third embodiment will now be described. Same reference numerals are given to those
components that are the same as the corresponding components of the first and second
embodiments. Such components will not be described in detail. In the third embodiment,
an example will be described in which an item presented on a display is selected using
a touchpad that is separate from the display. The operations performed on the touchpad
include a short tap, a long tap, a swipe, and a double tap (consecutive short taps).
In the third embodiment, the touch sensor device 10 is configured to distinguish a
short tap, a long tap, a swipe, and a double tap from one another.
[0042] As illustrated in Fig. 1, a touchpad 30 is arranged on a center console. In this
case, a display (not illustrated) is arranged in the dashboard instead of the touch
panel 11.
[0043] The touchpad 30 has the same configuration as the touch sensor device 10 of the second
embodiment and includes the touch panel 11, the electrodes 12, and the control unit
13. Since the touchpad 30 and the touch sensor device 10 have the same configuration,
the touchpad 30 will not be described in detail.
[0044] As illustrated by the broken lines in Fig. 2, the memory 13a of the control unit
13 stores a second operation determination time used to determine whether the touch
operation performed on the touch panel 11 is a short tap (single tap) or a double
tap. The second operation determination time is a value compared with the time during
which a non-touched state is detected and set in advance based on experiments or the
like.
[0045] Further, the control unit 13 uses the time counter 14 to measure the time during
which a non-touched state is detected (hereinafter, also referred to as "non-touched
state detection time"). That is, in the third embodiment, the time counter 14 measures
the time during which a touched state is detected and the time during which a non-touched
state is detected. The measurement value of the time counter 14 is reset when a touched
state shifts to a non-touched state and when a non-touched state shifts to a touched
state.
[0046] After expression (1) and expression (4) are both satisfied (i.e., after touch operation
corresponding to single tap is performed), the control unit 13 determines whether
or not a touch operation performed on the touch panel 11 has been completed based
on whether or not expression (6), which is illustrated below, is satisfied. That is,
through the determination of expression (6), the control unit 13 determines whether
a single tap is performed or a double tap is performed.
[Operation of Touchpad]
[0047] The operation of the touchpad 30 will now be described with reference to the flowchart
of Fig. 5 that illustrates the processing executed by the control unit 13. The processing
is executed when expression (1) is satisfied.
[0048] Referring to Fig. 5, when expression (1) is satisfied, the control unit 13 calculates
the first OFF determination threshold value from the maximum capacitance (step S1)
and then determines whether or not expression (4) is satisfied (step S2). Here, in
the same manner as the first and second embodiments, the control unit 13 sets the
first OFF determination threshold value to the value obtained by dividing the maximum
capacitance by the set value (e.g., two). Then, when detecting a non-touched state
based on expression (3), the control unit 13 determines whether or not expression
(4) is satisfied.
[0049] When step S2 is YES, that is, when expression (4) is satisfied, this indicates that
a touch operation corresponding to a single tap has been performed. In this case,
the control unit 13 determines whether or not expression (6) is satisfied (step S3).
[0050] When step S3 is YES, that is, when expression (6) is satisfied, this indicates that
after a touch operation corresponding to a single tap ends, a touch operation has
been performed once more within a second operation determination time. That is, the
satisfaction of expression (6) indicates that the capacitance at the electrode 12
has increased within the second operation determination time from when the capacitance
became lower than the first OFF determination threshold value. In this case, the control
unit 13 detects and obtains a new maximum capacitance and calculates a new first OFF
determination threshold value (step S4). Then, the control unit 13 determines whether
or not expression (4) is satisfied (step S5).
[0051] When step S5 is YES, that is, when expression (4) is satisfied, the control unit
13 generates a signal indicating that the operation performed on the touch panel 11
is a double tap (step S6). Then, the control unit 13 ends the series of processes.
[0052] When step S3 is NO, that is, when expression (6) is not satisfied, the control unit
13 generates a signal indicating that the operation performed on the touch panel 11
is a single tap (step S7). Then, the control unit 13 ends the series of processes.
[0053] When step S2 is NO or step S5 is NO, that is, when expression (4) is not satisfied,
the control unit 13 determines whether or not the operation performed on the touch
panel 11 is a swipe or a long tap and then generates a signal indicating the determination
(step S8). Then, the control unit 13 ends the series of processes. The process of
step S8 performed by the control unit 13 has been described in the second embodiment
and thus will not be described here in detail.
[0054] In addition to the advantages of the first and second embodiments, the third embodiment
has the advantages described below.
(7) The control unit 13 compares the second operation determination time and the non-touched
state detection time to determine whether the operation performed on the touch panel
is a single tap (short tap) or a double tap. This allows a signal tap and a double
tap to be distinguished from each other.
(8) The control unit 13 sets the first OFF determination threshold value to a value
obtained by dividing the maximum capacitance by a set value (e.g., two). When a double
tap is quickly performed on the touch panel 11, the capacitance at an electrode 12
increases before the capacitance sufficiently decreases. Thus, as illustrated in Fig.
6, when the OFF determination threshold value (first off determination threshold value)
is a fixed value like in the prior art, a quick double tap would be determined as
a long tap or a swipe. In the present example, the first OFF determination threshold
value is set to a value obtained by dividing the maximum capacitance by a set value
(e.g., two). Thus, even when a quick double tap is performed, the control unit 13
is able to detect the double tap.
[0055] It should be apparent to those skilled in the art that the present invention may
be embodied in many other specific forms without departing from the spirit or scope
of the invention. Particularly, it should be understood that the present invention
may be embodied in the following forms.
[0056] The touch sensor device 10 in the first and second embodiments may be realized as
the touchpad 30 of the third embodiment.
[0057] The touch sensor device 10 in the first and second embodiments may detect a double
tap in the same manner as the third embodiment.
[0058] In each of the above embodiments, the first OFF determination threshold value is
set to a value obtained by dividing the maximum capacitance by a first predetermined
set value but may be set to a value obtained by subtracting a second predetermined
set value from the maximum capacitance. That is, the first OFF determination threshold
value only needs to be smaller by a predetermined value, which is set in advance,
than the maximum capacitance detected during a touched state. In any case, the first
OFF determination threshold value is set based on the present maximum capacitance.
The first predetermined set value (or second predetermined set value) is set so that
the range of differences in the finger separation distance when determining a non-touched
state based on the first OFF determination threshold value is small and not influenced
by user characteristics. This reduces the influences resulting from the characteristics
of the user operating the touch sensor device 10 and improves the operation detection
accuracy.
[0059] In each of the above embodiments, the first OFF determination threshold value is
set to a value obtained by dividing the maximum capacitance by "2", which is the first
predetermined set value. However, the first predetermined set value, which is used
to calculate the first OFF determination threshold value, may be any value that is
greater than "1 ". The capacitance generated at the electrode 12 varies in accordance
with the transmittance, which is based on the material of the touch panel 11, and
the distance to the fingertip, which is based on the thickness of the touch panel
11. Thus, it is preferable that the first predetermined set value be set based on
experiments and simulation results.
[0060] In each of the above embodiments, the ON determination threshold value is set taking
into consideration the increase amount of the capacitance. Instead, the ON determination
threshold value may be set to a unique capacitance.
[0061] In each of the above embodiments, the determination results of the touch sensor device
10 are used for an air conditioner. Instead, the determination results may be used,
for example, to set the volume or frequency of the audio device or to set a navigation
system. When used for a navigation system, a touch sensor device that detects the
touched position may be employed. Further, the touch sensor device 10 may be employed
as a touch sensor device that detects whether or not a vehicle door handle has been
touched.
[0062] In each of the above embodiments, the increase amount of the capacitance when detecting
a touched state is obtained by subtracting the preceding value of the capacitance
at an electrode from the present value. Instead, the increase amount of the capacitance
may be obtained by subtracting the average value of a plurality of previous detection
values from the present value.
[0063] In each of the above embodiments and modified examples, the touch sensor device 10
is used for a vehicle. Instead, the touch sensor device 10 may be used, for example,
in a system used to lock and unlock a house.
[0064] In each of the above embodiment, the touch sensor device 10 is arranged in a dashboard
but may be arranged at a different position. For example, the touch sensor device
may be arranged in a center console or a steering wheel.
[0065] In each of the above embodiments, as illustrated in Fig. 7, the electrodes 12 may
be separated from the touch panel 11 as long as the electrodes 12 are arranged at
the inner side of the touch panel 11.
[0066] In the second embodiment, the second OFF determination threshold value is a fixed
value but may be a variable value that is set based on the maximum capacitance in
the same manner as the first OFF determination threshold value. For example, when
the first OFF determination threshold value is set to a value obtained by dividing
the maximum capacitance by "2", the second OFF determination threshold value may be
set to a value obtained by dividing the maximum capacitance by "3". The second OFF
determination threshold value only needs to be a value that is at least lower than
the first OFF determination threshold value and slightly greater than the total capacitance
of every one of the electrodes 12 in a non-touched state.
[0067] In the second embodiment, the determination of a long tap and a swipe is performed
only once. However, the determination of whether a long tap or a swipe may be performed
a number of times by comparing the previous touched position and the present touched
position whenever calculating a new touched position.
[0068] In the third embodiment, a third OFF determination threshold value dedicated for
the determination of a double tap may be set to a value that is greater than at least
the first OFF determination threshold value. In this case, after expression (1) is
satisfied, the control unit 13 determines that a double tap has been performed when
three conditions are satisfied, which are (A) the capacitance is lower than at least
the third OFF determination threshold value, (B) expression (1) is satisfied again,
and (C) the capacitance is lower than the first OFF determination threshold value.
In this case, during a double tap, the capacitance does not have to be lower than
the first OFF determination threshold value at the first tap of the double tap. Thus,
even when a quicker double tap is performed, the control unit 13 is able to correctly
detect the double tap.
[0069] In each of the above embodiments, the ON determination threshold value may be a variable
value or a fixed value. When the ON determination threshold value is a fixed value,
the computation load on the control unit 13 is smaller than when the ON determination
threshold value is a variable value. Thus, the control unit 13 may be simplified.
[0070] In each of the above embodiments, the ON determination threshold value is set as
a reference value that is compared with the increase amount of the capacitance (i.e.,
relative value). Instead, the ON determination threshold value may be set as a reference
value that is compared with the present value of the capacitance (i.e., absolute value).
[0071] The processing executed by the control unit 13 of each of the above embodiments may
be realized by an exclusive hardware circuit or a group of commands (software) executed
by a computer processor such as a CPU. When using software, the computer processor
reads the commands from a non-transitory computer-readable medium (e.g., working memory
such as a RAM) to execute processing for determining touching of the touch panel.
[0072] In this case, the group of commands includes a command for having a computer processor
detect changes in the capacitance generated at an electrode 12 in accordance with
the approach of a finger and a command for having the computer processor determine
touching of the touch panel 11 from changes in the capacitance. When the computer
processor determines whether or not the touch panel 11 has been touched, the group
of commands includes a command for having the computer processor detect the maximum
capacitance generated at an electrode 12 during the detection of a touched state and
a command for having the computer processor set the first OFF determination threshold
value, which is used to detect a non-touched state, to a value that is lower than
the maximum capacitance by a predetermined value, which is set in advance.
[0073] Preferably, the group of commands include a command for having the computer processor
set the first OFF determination threshold value to a value obtained by dividing the
maximum capacitance by a first predetermined set value or by subtracting a second
predetermined set value from the maximum capacitance.
[0074] Preferably, the group of commands includes a command for having the computer processor
determine whether or not the touching of the touch panel is a short tap by comparing
a predetermined first operation determination time with the time during which the
touched state is detected.
[0075] Preferably, the group of commands includes a command for having the computer processor
determine a touched position on the touch panel; determine whether the touching of
the touch panel is a long tap or a swipe from time changes of the touched position;
and when determining that the touch panel has been swiped, determine whether or not
the touch panel is still being swiped based on a second OFF determination threshold
value which is lower than the first OFF determination threshold value.
[0076] Preferably, the group of commands includes a command for having the computer processor
determine whether or not a double tap has been performed on the touch panel when the
capacitance generated at the electrode increases within a second operation determination
time, which is set in advance, from when the capacitance becomes lower than the first
OFF determination threshold value.
[0077] Preferably, the group of commands includes a command for having the computer processor
compare a present value of the capacitance generated at the electrode with a previous
value of the capacitance generated at the electrode, and determine that the non-touched
state has shifted to the touched state when an increase amount of the capacitance
becomes greater than an ON determination threshold value which is set in advance.
[0078] Preferably, the group of commands includes a command for having the computer processor
determine that the non-touched state has shifted to the touched state when a present
value of the capacitance generated at the electrode becomes greater than an ON determination
threshold value which is set in advance to a fixed value.
[0079] The present examples and embodiments are to be considered as illustrative and not
restrictive, and the invention is not to be limited to the details given herein
[0080] A touch sensor device (10) includes an electrode (12), which is located at an inner
side of a touch panel (11), and a control unit (13). The control unit (13) detects
a change in a capacitance generated at the electrode (12) when a finger approaches
the electrode (12) to determine whether or not the touch panel (11) has been touched
from the change in the capacitance. The control unit (13) detects a maximum capacitance
generated at the electrode (12) during detection of a touched state and set a first
OFF determination threshold value, which is used to detect a non-touched state, to
a value that is lower than the maximum capacitance by a predetermined value which
is set in advance.
1. A touch sensor device (10) comprising:
an electrode (12) located at an inner side of a touch panel (11); and
a control unit (13) configured to detect a change in a capacitance generated at the
electrode (12) when a finger approaches the electrode (12) and determine whether or
not the touch panel (11) has been touched from the change in the capacitance;
the touch sensor device (10) characterized in that:
the control unit (13) is configured to detect a maximum capacitance generated at the
electrode (12) during detection of a touched state and set a first OFF determination
threshold value, which is used to detect a non-touched state, to a value that is lower
than the maximum capacitance by a predetermined value which is set in advance.
2. The touch sensor device (10) according to claim 1, wherein the control unit (13) is
configured to set the first OFF determination threshold value to a value obtained
by dividing the maximum capacitance by a first predetermined set value.
3. The touch sensor device (10) according to claim 1, wherein the control unit (13) is
configured to set the first OFF determination threshold value to a value obtained
by subtracting a second predetermined set value from the maximum capacitance.
4. The touch sensor device (10) according to any one of claims 1 to 3, wherein the control
unit (13) is configured to determine whether or not the touching of the touch panel
(11) is a short tap by comparing a first operation determination time, which is set
in advance, with a time during which the touched state is detected.
5. The touch sensor device (10) according to claim 4, wherein the control unit (13) is
configured to
determine a touched position on the touch panel (11),
determine whether the touching of the touch panel (11) is a long tap or a swipe from
time changes of the touched position, and
when determining that the touch panel (11) has been swiped, determine whether or not
the touch panel (11) is still being swiped based on a second OFF determination threshold
value which is lower than the first OFF determination threshold value.
6. The touch sensor device (10) according to claim 4 or 5, wherein the control unit (13)
is configured to determine whether or not a double tap has been performed on the touch
panel (11) when the capacitance generated at the electrode (12) increases within a
second operation determination time, which is set in advance, from when the capacitance
becomes lower than the first OFF determination threshold value.
7. The touch sensor device (10) according to any one of claims 1 to 6, wherein the control
unit (13) is configured to compare a present value of the capacitance generated at
the electrode (12) with a previous value of the capacitance generated at the electrode
(12), and determine that the non-touched state has shifted to the touched state when
an increase amount of the capacitance becomes greater than an ON determination threshold
value which is set in advance.
8. The touch sensor device (10) according to any one of claims 1 to 6, wherein the control
unit (13) is configured to determine that the non-touched state has shifted to the
touched state when a present value of the capacitance generated at the electrode (12)
becomes greater than an ON determination threshold value which is set in advance to
a fixed value.
9. A controller (13) for controlling a touch sensor device (10) including a touch panel
(11) to which an electrode (12) is arranged, the controller (13) comprising:
a computer processor including a non-transitory computer readable medium that stores
a group of commands for executing a process that determines whether or not the touch
panel (11) has been touched, wherein the group of commands include
a command for having the computer processor detect a change in a capacitance generated
at the electrode (12) when a finger approaches the electrode (12), and
a command for having the computer processor determine whether or not the touch panel
(11) has been touched based on the change in the capacitance, wherein the command
for having the computer processor determine whether or not the touch panel (11) has
been touched includes
a command for having the computer processor detect a maximum capacitance generated
at the electrode (12) during detection of a touched state, and
a command for having the computer processor set a first OFF determination threshold
value, which is used to detect a non-touched state, to a value that is lower than
the maximum capacitance by a predetermined value which is set in advance.